ИСТИНА

The degree of interest to the Arctic is very high. There are several reasons for this tendency. Firstly, global warming and it’s regional consequences: increasing in air temperature and river flow, Arctic ice melting etc. Secondly, new perspectives in the development of Arctic natural resources and large-scale projects that are already being implemented. Third, changes in the level of anthropogenic impact on the Arctic ecosystems, or, conversely, the impact of changing conditions (for example, natural hazards) on the socio-economic complex. The tasks of the present study were to determine the composition and characteristics of hydrological hazardous on the rivers of the Arctic zone of Russia, their long-term climatic and anthropogenic changes. The work was carried out under the RFBR grant №18-05-60021. In AZR the main losses connected with river floods and storm surges. River floods here usually accompany spring-summer high water period. It is characterized by maximum water discharges and massive ice jams, relatively fast and very high jumps in the water level. The average increase in the water level is 3–8 m, while the maximum values are 20–25 m in the lower reaches of the Yenisei and Lena rivers, 33 m – Tunguska River. Extreme high water levels lead to flooding of settlements, industrial facilities, roads, deterioration of water quality. The agglomeration of Arkhangelsk city suffered from floods historically. They were ~ 71 events of varying intensity here just from 1900 to 2015. But the long-term struggle with ice jams helped to stop the death of people, reduce the frequency and magnitude of floods. At the mouth of the Pechora River ~ 34 serious river floods were discovered (1912-2015). In total approximately 80 Arctic settlements are suffered from flooding. Annual spills of river waters do not lead to damage in low developed or completely undeveloped territories. Storm surges in the river mouths usually occur during fall period. The magnitude of surges rarely exceeds 3 m, whereas the maximum tides may be 1.5–3 times higher (the largest value (8–9 m) at the Mezen River mouth). Surge flooding are short-term and usually local events, but no less dangerous. Such event in November 2011 lasted less than 2 days, but almost 50 km of land were flooded. Damage to Arkhangelsk and Severodvinsk amounted to $ 1.5–2 million. The situation with surges in the Arctic is worsening due to rising sea level and a decrease in the sea ice cover, increased synoptic instability, and the lack of effective protection. Low water levels during wind drifts and low water period, sea water intrusion, winter freezing of rivers, natural and anthropogenic pollution of river waters and disruption of water supply to settlements and industry during such events, process of abrasion intensification on river benches and sea shores composed by permafrost, no less dangerous hydrological phenomena in the Russian Arctic. They can also have negative environmental consequences. Until recently, very little was known about these events, compared to floods and ice jams. But thanks to research, it was possible to learn a lot about these processes, to evaluate some of their characteristics, to study the causes and peculiarities of their spatial and temporal variability. These are new and important results that help the efficient, safe and sustainable development of water bodies in the Russian Arctic and their coasts.